1. Field of the Invention
The present invention relates generally to the art of electroplating and more specifically to an electroplating method in which the plating bath is treated prior to and/or during the plating process. Still more specifically, the invention relates to electroplating wherein electromagnetic radiation is injected into the plating bath, most preferably in the radio frequency range and with injection occurring through a conductor in direct contact with the plating bath.
2. Description of the Prior Art
Numerous systems have been proposed over the years for treating aqueous solutions to obtain improvements in certain methods or to achieve certain properties for the treated solution. Several examples of the types of treatment include those involving the use of electromagnets, permanent magnets, ultrasound, electrostatic fields and the like. While some within the scientific community are convinced of the effectiveness of such treatment methods, considerable skepticism remains, and the devices which have been marketed have not received a high degree of commercial success. The types of applications with which such treatment methods have been employed are also widely varied. Some will be described below in connection with the description of certain specific prior art, but generally, they have included the treatment of aqueous solutions to prevent scaling in boilers, cooling towers and the like; the treatment of emulsions; the treatment of certain non-aqueous materials such as fuels for increasing the fuel burning efficiency thereof; the treatment of automobile radiator fluid; and other diverse applications.
Several representative samples of such prior art treatment systems will now be disclosed briefly, but particular attention should be direct to the Morse patents, the backgrounds provided therein, and the references cited against same.
One such treatment device, called the Ion Stick, utilizes the application of an electrostatic field, as illustrated in a brochure entitled "The Ion Stick", copies of which are provided with this specification. This device is a non-chemical, non-polluting electrostatic water treater energized by its own power pack. Another electrostatic treatment method and device is disclosed in U.S. Pat. No. 4,545,887 issued Oct. 8, 1985 to Arnesan, et al.
Other devices employ fixed magnets for water treatment. Examples include U.S. Pat. No. 4,808,306, issued Feb. 28, 1989 to Mitchell and entitled "Apparatus for Magnetically Treating Fluids", and U.S. Pat. No. 4,367,143, issued to Carpenter on Jan. 4, 1983 for "Apparatus for Magnetically Treating Liquid Flowing Through a Pipe and Clamping Means Therefor".
A different magnet arrangement for water treatment is disclosed in U.S. Pat. No. 4,888,113, issued to Holcomb on Dec. 19, 1989 for "Magnetic Water Treatment Device". In this patent, Holcomb discusses the use of a plurality of rectangular magnets attached to the exterior of a pipe. The magnets are arranged in pairs adjacent the pipe such that the positive pole of one pair is oriented to one end of the support housing and the negative pole is oriented toward the other end of the housing. Another similarly constructed housing is secured to the opposite side of the pipe, but reversed with respect to magnet polarity. Thus, the positive pole of the first set faces the negative pole of the second set to cause an "attractive" mode of magnetic flux treatment. Applications such as scale prevention, as well as use in washing machines, swimming pools, ice rinks, livestock watering, and coffee brewing are suggested. The patent also suggests that the taste of treated water is superior to that of untreated water. The patent further mentions that the magnetic force fields can be generated through wound iron coils coupled to a DC generator.
The assignee of the present invention is the owner of several patents relating to electro-magnetic water treatment devices, including Stickler et al., U.S. Pat. No. 4,746,425, issued May 24, 1988 for "Cooling System for Magnetic Water Treating Device" and Stickler et al., U.S. Pat. No. 4,659,479, issued Apr. 21, 1987 for "Electromagnetic Water Treating Device". Both use a pipe core of alternating magnetic and non-magnetic sections with an electromagnet surrounding the pipe through which the fluid to be treated passes.
The prior art is replete with devices that employ electromagnetic energy for water treatment. Many such devices employ electromagnetic energy at a fixed frequency. Examples of such fixed frequency devices are U.S Pat. No. 4,407,719, issued Oct. 4, 1983 to Van Gorp and entitled "Magnetic Water Treatment Apparatus and Method of Treating Water"; U.S. Pat. No. 4,288,323, issued Sep. 8, 1981 to Brigante and entitled "Free Flow Non-Corrosive Water Treatment Device"; and U.S. Pat. No. 2,596,743, issued May 13, 1952 to Vermeiren and entitled "Electric Device".
Several other United States patents disclose specific methods and/or devices which employ varied and/or mixed frequency electromagnetic energy. For example, U.S. Pat. No. 3,511,776, issued to Avanpoto, discloses a method of using various wavelengths of electromagnetic energy, mostly within the ultraviolet and x-ray spectra, to cause ionic species within a flowing water system to become more susceptible to attraction by a subsequent magnetic field.
U.S. Pat. No. 3,625,884, issued to Waltrip, discloses a sewage treatment method which employs multiple signal generators to simultaneously provide audio frequency and/or radio frequency energy at a number of different frequencies. The frequency output of each separate signal generator may be selected on the basis of the mineral content of the untreated sewage.
U.S. Pat. No. 4,365,975, issued to Williams et al., discloses a method of recovering alkali metal constituents from coal gasification residues by subjecting the residues to electromagnetic energy in the radio frequency-microwave (0.1 to 10.sup.5 MHz) range. Such electromagnetic radiation is purported to facilitate extraction of the metal.
Another treatment system is disclosed in a patent owned by the assignee of the present invention, namely Larson et al., U.S. Pat. No. 4,865,747, issued Sep. 12, 1989 for "Electromagnetic Fluid Treating Device and Method". An electromagnetic field having a voltage which operates in the range of 1 KHz to 1,000 MHz is applied to a non-ferromagnetic conduit in which a ferromagnetic core is mounted. The core acts as a sacrificial anode and as a receiving antenna for the radio frequency radiation.
Also designed for use in fighting scale formation, a device known as the "Aquabel" has been sold and purportedly involves an electronic circuit producing electromagnetic signals which are transmitted into water through cables coiled in a spiral shape around the water line. A copy of a brochure relating to this device is included with this specification.
Electromagnetic radiation, in the form of microwave radiation, is discussed as a treatment mechanism for emulsions in U.S. Pat. No. 4,582,629, issued to Wolf on Apr. 15, 1986.
An electromagnetic process for altering the energy content of dipolar substances is disclosed in British Patent 417,501, issued Dec. 28, 1934, to Johnson. According to Johnson, irradiating colloids with electromagnetic energy having a wavelength characteristic of the colloid will alter the mobility and viscosity of the colloid. Also, treatment of organic substances such as milk or meat will prevent aging of the substance. Another use is the treatment of living organic matter, such as bean seeds, to increase their growth.
Other methods and devices which involve the treatment of water using electromagnetic energy having a variable frequency include German Patent 463,844 issued Aug. 6, 1928 to Deutsch and British Patent 606,154, issued Aug. 6, 1948, to Brake.
Yet another type of scale prevention is disclosed in U.S. Pat. No. 1,773,275, issued Aug. 19, 1930 to Neeley, which discloses supplying an electric current to the water by subjecting the water to electromagnetic fields or by having it come into contact with electrically charge surfaces.
Another water treating technique is that disclosed in U.S. Pat. No. 4,865,748, issued Sep. 12, 1989 to D. Morse and entitled "Method and System for Variable Frequency Electromagnetic Water Treatment". In this patent, a conductor in direct contact with a fluid to be treated is coupled to a generator of electromagnetic radiation, preferably in the radio frequency range. According to the patent, the radiation is injected at a frequency which is related to the electromagnetic radiation absorption or emission profile of the particular system being treated. This patent focuses on the use of that device for the elimination and prevention of scale buildup in boiler systems and the like. The Morse patent is also owned by the assignee of the present invention. A continuation-in-part of the aforementioned Morse patent issued as U.S. Pat. No. 4,963,268 on Oct. 16, 1990.
The assignee of the present invention has three pending applications relating to use of devices, generally similar to the devices described in the Morse patents. These include U.S. patent application Ser. No. 07/621,619, filed Dec. 3, 1990 and entitled "Ice Making Water Treatment", U.S. patent Ser. No. 07/531,021, filed May 31, 1990 and entitled "Beverage Brewing System", and U.S. patent Ser. No. 07/564,790, filed Aug. 8, 1990 and entitled "Filtration Cleaning System".
Many electroplating systems are known to the art which involve the deposition onto a substrate of a layer of metal from a plating solution. Some systems use constant injection of electrical energy to cause plating to occur, and pulse plating is also known, wherein the current is interrupted 600 to 10,000 times per second to improve plating performance. See the article "An Overview of Pulse Plating", by Osero, furnished with this specification.